Scanning probe microscope

ABSTRACT

A scanning probe microscope uses two different scanners (also called “scanning stages”) that are completely detached each from the other, and are physically separated by a stationary frame. One scanner (called “x-y scanner”) scans a sample in a plane (also called “x-y plane”), while the other scanner (called “z scanner”) scans a probe tip (which is supported at a free end of a cantilever) in a direction (also called “z direction”) perpendicular to the plane. Detachment of the two scanners from one another eliminates crosstalk.

BACKGROUND OF THE INVENTION

[0001] The Scanning Probe Microscope (SPM) is a powerful instrument inthe nanometer scale science and technology. Among the many variations ofSPM, the Atomic Force Microscope (AFM) is the most widely used and themost fundamental version. One prior art AFM is described in an articleby G. Binnig, C. Quate, and Ch. Gerber in Phys. Rev. Lett. 56, 930(1986). AFM has evolved since then, refining its capabilities andconveniences. In a commonly used configuration, a prior art AFM has amicro-machined cantilever with a sharp tip on its edge, and the AFMscans the sample or the cantilever with a piezoelectric tube. Thedeflection of the cantilever is measured by the AFM casting a laser beamon the cantilever and detecting the reflected beam with a positionsensitive photo detector (PSPD). (See the article by G. Meyer and N. M.Amer, in Appl. Phys. Lett. 53, 2400 (1988).)

[0002] In such a configuration, the AFM has a high vertical sensitivityand is relatively easy to implement. In order to adjust the incidentlaser beam to fall on the cantilever and make the reflected beam hit thecenter of PSPD, an aligning mechanism with fine screws is used. Aprobing unit, including such an aligning mechanism plus the laser, PSPD,and cantilever, has considerable mass and it is difficult for the AFM toscan the probing unit at sufficiently high speed while maintainingaccuracy. In the prior art, typical x scan speed is in the range of 0.1Hz˜4 Hz and necessary z servo bandwidth is 100 Hz˜1 kHz. Such scan speedis acceptable but not satisfactory for the reasons discussed below.Therefore in certain conventional AFMs, the probing unit was keptstationary and the sample was scanned along x, y and z axes. See U.S.Pat. Nos. 5,157,251 granted to Albrecht et al. and 5,237,859 granted toElings et al., both of which are incorporated by reference herein intheir entirety.

[0003] However, large samples, such as large silicon wafers, cannot bescanned fast enough e.g. 1 KHz in z direction for sufficient verticalservo frequency response. For a description of this problem, see forexample, U.S. Pat. No. 5,463,897 column 2, line 19-24. See also anarticle by P. K. Hansma, B. Drake, D. Grigg, C. B. Prater, F. Yashar, G.Gurley, and V. Elings, S. Feinstein, and R. Lal, J. Appl. Phys. 76, 796(1994). The cantilever may be scanned while ensuring that the laser beamfollows the cantilever motion to solve this problem. A simple method isminiaturizing the aligning mechanism, and scanning the whole probingunit. Such a scanning probe is implemented in the “AutoProbe M5”scanning probe microscope available from TM Microscopes, Veeco MetrologyGroup, 1171 Borregas Avenue, Sunnyvale, Calif. 94089, USA and describedon the Internet at www.tmmicro.com.

[0004] However, such a miniaturized probing unit still has aconsiderable mass and it degrades the z servo response. It is alsoinconvenient to align the laser beam with tiny screws and a special toolhad to be used. Another method is attaching lenses on the tube scannersuch that the laser beam follows the cantilever motion and the reflectedbeam hits the same point on the PSPD. Such a tube scanner is implementedin the “Dimension 3100” microscope available from Digital Instruments,Veeco Metrology Group, 112 Robin Hill Road, Santa Barbara, Calif. 93117and described on the Internet at www.di.com. See also U.S. Pat. No.5,463,897 granted to Prater et al. which is incorporated by referenceherein in its entirety. See also the article by P. K. Hansma, B. Drake,D. Grigg, C. B. Prater, F. Yashar, G. Gurley, and V. Elings, S.Feinstein, and R. Lal, J. Appl. Phys. 76, 796 (1994). However in thismethod, the laser beam does not perfectly follow the cantilever and thereflected beam does not remain on the exact same point on the PSPD,causing measurement errors and tracking force variations during x-yscan.

[0005] In addition, most AFMs have the common problems of scanningerrors and slow scanning speed. A piezoelectric tube-based scannercommonly used in the prior art is not an orthogonal 3-dimensionalactuator that can be moved in any of the three dimensions x, y and zindependent of one another. Since the x-y motion relies on the bendingof the tube, there is non-linearity and cross talk between x-y and zaxes. AFMs can use position sensors to correct the intrinsicnon-linearity of the piezoelectric tube as described in U.S. Pat. No.5,210,410 granted to Barrett, and incorporated by reference herein inits entirety; see also an article by R. Barrett in Rev. Sci. Instrum.62, 1393 (1991). However, z cross talk from flexing the tube cannot beeliminated and it causes background curvature effect and measurementerrors. Using a tripod scanner does not improve the non-linearity andcross talk problem much. Furthermore the piezoelectric tube-basedscanner has low resonance frequency (typically below 1 kHz) and does nothave high force to drive a conventional probing unit at high speed.

[0006] In order to improve the orthogonality of the scanner, U.S. Pat.Nos. 6,310,342, 6,057,546 and 5,854,487 all granted to Braunstein, etal. (each of which is incorporated by reference herein in its entirety)describe the prior art use of a flexure stage for x-y scanning. However,since the z scanner described by Braunstein et al. is attached to thex-y scanner, the z scanner cannot move faster than the resonancefrequency of the x-y scanner, which is about 100 Hz.

[0007] As mentioned above, the scanning speed of AFM is important. Thescanning speed of AFM is usually limited by the z servo frequencyresponse as described below. The z scanner needs to follow the samplefeatures with appropriate feedback controller. As the scan speed in xdirection is increased, the z scanner has to move up and down faster,requiring higher bandwidth in z servo system. However, the verticalservo frequency response cannot be higher than the resonance frequencyof the z scanning system. z-scanning system means the z scanner and thesupporting structure for the z scanner plus whatever the z scanner hasto move in z direction. The resonance frequency of the z scanning systemis reduced as more mass is loaded on to the z scanner. If the z scannerhas higher push-pull force, the resonance frequency is reduced less.

[0008] Typical AFM has a few hundred Hz bandwidth in z servo system.Let's consider the case of 512 Hz. If we want to take a 256×256 pixelimage, we can scan 1 Hz in x direction. (forward 256 plus backward 256)Of course, we can scan faster if the sample is smooth so that there isnot much height variation between adjacent data points. Since we need tocollect 256 lines of data, it takes 256 seconds (about 4 min.) to finishone scan. 4 min is a long time, and it is important to increase the scanspeed. Typically, x-y scan speed is not limited by the x-y scannerbandwidth but limited by the z servo frequency response.

[0009] In AFMs, it is necessary to replace the cantilever frequently.The micro-machined cantilever is attached on a small chip (2×4 mm), andit is difficult to handle even with a tweezers. In order to improve thehandling, the cantilever chip was mounted on an aluminum plate in theprior art. See U.S. Pat. No. 5,376,790 granted to Linker et al.; Seealso TM Microscopes CP, M5. Such a prior art plate had three slots,whose angles are 120° apart. These slots make contact with three balls.A spring clip was used to hold the chip mount. In another prior art (seeTM Microscopes Explorer; see also U.S. Pat. No. 5,319,960 granted toGamble et al.), a magnet was used to hold the chip mount but the chipmount sit directly on the magnet, which does not ensure the samecantilever position after replacement. Young et al. (see U.S. Pat. No.5,705,814) have used a complicated method to align the cantilever.

[0010] Furthermore, the AFM head needs to be removed from the AFM framefrom time to time. For convenient mount and un-mount of the AFM head, adovetail groove has been made on the AFM head and a dovetail rail hasbeen attached on the frame in the prior art. See, for example, TMMicroscopes, CP; Digital Instruments, Dimension 3100. Since the AFM headneeds to be firmly mounted on the frame, a fastening screw was used totighten the dovetail.

SUMMARY

[0011] A scanning probe microscope in accordance with the invention usestwo different scanners that are completely detached each from the other,and are physically mounted at separate locations on a stationary frame.One scanner (called “x-y scanner”) scans a sample in a plane (alsocalled “x-y plane”), while the other scanner (called “z scanner”) scansa probe tip (which is supported at a free end of a cantilever) in adirection (also called “z direction”) perpendicular to the plane.Detachment of the two scanners from one another ensures that eachscanner can be moved (relative to the frame) without affecting the otherscanner.

[0012] Depending on the embodiment, the scanning probe microscope mayinclude a light source to illuminate a cantilever that supports theprobe tip, and a photodetector to receive a portion of light reflectedby the cantilever, thereby to sense the deflection of the cantilever.The light source and the photodetector may be supported at locationshorizontally separated from a vertical line of movement of the probetip. In one embodiment, a reflective element (such as a prism) islocated along the vertical line of movement of the probe tip, and thelight source is horizontally aimed at the reflective element, so thatthe same spot on the cantilever is illuminated (in the downwarddirection in this embodiment), regardless of vertical movement of thecantilever by the scanner.

[0013] In such an embodiment, light reflected by the cantilever may bedirected to the photodetector via one or more optical elements. Forexample, a mirror may be used to reflect light from the cantileverhorizontally on to the photodetector. In this example, an error in theposition detected by the photodetector due to the z scanner movement maybe corrected by software. As another example, two parallel mirrorslocated horizontally across from one another may be used between thecantilever and the photodetector, so that light reflected by thecantilever is at the same angle as light incident on the photodetector.Therefore, in this example, the same spot on the photodetector (e.g. thecenter) is illuminated, regardless of vertical movement of the z scanner(on which the cantilever and photodetector are mounted).

[0014] Also depending on the embodiment, the light source, thephotodetector and any intermediate optical elements in a paththerebetween may be located vertically close to the cantilever, toaccommodate an objective lens and a camera along a line of movement ofthe probe tip, thereby to provide a direct on-axis view of a sampleunder evaluation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 illustrates, in a conceptual diagram, a scanning probemicroscope with a z scanner separated from an x-y scanner in accordancewith one aspect of the invention.

[0016] FIGS. 2-4 illustrate, in side elevation views, the locations of alaser, a prism, a cantilever beam, a steering mirror and a photodetectorall used in the scanning probe microscope FIG. 1, in three differentembodiments.

[0017]FIG. 5A illustrates, in a side elevation view, a scanning probemicroscope including optical elements for direct on-axis view of thesample under evaluation, in accordance with another aspect of theinvention.

[0018]FIG. 5B illustrates, in a cross-sectional view in the direction5B-5B in FIG. 5A, flexible mounting of an on-axis optics module on to afocusing stage by a bracket of one embodiment.

[0019]FIGS. 5C, 5D and 5E illustrate, in a side view, a front view, anda top view respectively, an assembly of a scanning probe microscope ofthe type illustrated in FIGS. 5A and 5B, including the x-y scanner andthe stationary frame.

[0020] FIGS. 6A-6C illustrate, in a side elevation view, an enlargedbottom view and a side view of the bottom, respectively, an end of aprobe arm configured for kinematic mounting of a cantilever chip mount.

[0021]FIG. 6D illustrates, in a plan view, a cantilever chip mount foruse with the probe arm of FIGS. 6A-6C.

[0022]FIGS. 6E and 6F illustrate, in a side elevation view and a bottomplan view respectively, an assembly of the cantilever chip mount withthe probe arm.

[0023] FIGS. 7A-7C illustrate, in a side elevation view, a top view, anda front elevation view respectively an assembly of a probe head to a zstage.

[0024]FIG. 7D illustrates, in an enlarged view, a use of a screw in theassembly of FIG. 7B to attach a handle.

DETAILED DESCRIPTION

[0025] A scanning probe microscope 30 in accordance with the inventionphysically separates a z scanner 10 from an x-y scanner 20, as shown inFIG. 1. Scanners 10 and 20 are mounted on a common frame 35 that isstationary, although in an alternative embodiment, they may be mountedon different frames. There is also a z-stage 73 between scanner 10 andscanner 20. The z-stage 73 is a one dimensional translation stage with astepper motor and is used to bring a probe tip (mounted on a cantileverthat in turn is mounted on a z scanner) close enough to a sample on asample chuck 50 so that the sample surface can be reached within zscanner range. Regardless of how they are mounted, the two scanners 10and 20 are physically detached from one another (i.e. are notmechanically coupled, except that both are coupled to a stationary frame35 and each provides motion relative to the frame independent of theother).

[0026] Such physical separation of x-y scanner 20 from z scanner 10, ina scanning probe microscope of the type described above, has a number ofadvantages over integration of both scanners into a single head asdescribed by Braunstein, et al. in U.S. Pat. Nos. 6,310,342, 6,057,546and 5,854,487. In contrast to use of Braunstein et al.'s head carryingthe two scanners, z scanner 10 (FIG. 1) can be moved much faster andmore accurately.

[0027] One embodiment of microscope 30 uses a two-dimensional flexurestage 20 to scan a sample chuck 50 (e.g. holding a silicon wafer) in x-ydirection only, and a one dimensional piezoelectric actuator 10 to scana probe cantilever 34 in the z direction only.

[0028] An example of flexure stage 20 is model P-730 stage availablefrom PI, http://www.pi.ws. Such a flexure stage 20 has a highorthogonality, and can scan large samples (˜2 kg) up to 100 Hz in x-ydirection. This scan speed is sufficient because the bandwidthrequirement for x-y axes is much lower than for z axis. In oneembodiment, a stacked piezoelectric actuator 10 used as z scanner has ahigh resonance frequency (>10 kHz) with high push-pull force whenappropriately pre-loaded.

[0029] In one embodiment, microscope 30 includes a laser 31, laser beamaligning mechanism (such as a prism) 32, and a photodetector (such as aposition sensitive photo detector (PSPD)) 33. Photodetector 33 issupported by z scanner 10 that also supports cantilever 34. Thisarrangement in microscope 30 is provided to ensure that a laser beamfalls on the same point on a cantilever 34, and the reflected beam hitsthe same point on the PSPD 33 regardless of the motion of z scanner 10.Therefore, only the deflection of cantilever 34 is monitored onphotodetector 33. In the embodiment of FIG. 2, laser 31 and laser beamaligning mechanism 32 are fixed on the probing head.

[0030] The laser beam from laser 31 is reflected by prism 32, both ofwhich are mounted on a glass plate 37. The angle of glass plate 37 (andtherefore of prism 32) relative to cantilever 34 can be adjusted by twoscrews 38A and 38B located on the two diagonal corners of a glass plateholder 39. Since the laser beam is falling on cantilever 34 from thevertical direction, the beam always hits the same point on cantilever34, regardless of motion of z scanner 10.

[0031] The reflected beam from cantilever 34 is bounced by a steeringmirror 40 and hits photodetector 33. Mirror 40 of FIG. 2 is supported bythe probing head 36, at a position offset from the vertical line passingthrough prism 32. The angle of steering mirror 40 can be slightlyadjusted by two screws 41 and 42 on its diagonal edges such that thebounced beam hits the center of PSPD 33. Since the steering mirror 40 isvertically mounted, the bounced beam always hits the same point on PSPD33, regardless of z scanner motion, and therefore only the deflection ofthe cantilever is detected by PSPD 33.

[0032] In one embodiment, to accommodate an optical microscope, aclearance is provided above the cantilever 34. For this purpose, theposition of PSPD 33 is lowered relative to laser 31 as shown in FIG. 3.Moreover, the steering mirror 40 is mounted at an angle to the vertical(e.g. 45°) such that the path of bounced laser beam becomes horizontalas shown in FIG. 3. However, in this configuration, the spot formed bythe bounced laser beam on the PSPD 33 changes, as z-scanner 10 moves.When z scanner 10 moves a distance h, there is an error of h(1−sin 2θ)in the position of the laser beam spot on the PSPD 33 as shown in FIG.3. This amount of error is very small compared to the amount of thelaser beam spot displacement when the cantilever 34 is deflected by h,because changing the angle of the reflected laser beam causes muchgreater displacement of the laser beam spot on PSPD (typically 500 timesmore). Please note that h is exaggerated very much in the drawing toillustrate the beam path change. For example, h is a very small amountlike a few nm to a few μm, while the length of the cantilever is about100 μm.

[0033] Of course, this error disappears in some embodiments wherein thesteering mirror 40 is attached to z scanner. However, scanning only thecantilever 34 and PSPD 33 with the z scanner in certain embodimentsincreases bandwidth as compared to also scanning the steering mirror 40which significantly increases mass and reduces the z-bandwidth.

[0034] Since z scanner motion h is a known quantity, it is possible tocompensate for error h(1−sin 2θ) in software. An alternative method isto eliminate such error by introducing another mirror 43 (FIG. 4) whoseangle is parallel to the angle of steering mirror 40 and the PSPD 33 isaimed at mirror 43. In the configuration of FIG. 4, second mirror 43exactly compensates the effect of first mirror 40, and therefore thelaser beam hits the same point on PSPD 33 regardless of z scannermotion.

[0035] Therefore, the space above prism 32 (FIG. 4) is now available forinstallation of a direct on-axis optical microscope, as shown in FIG.5A. The optical path from the sample held by a sample chuck (not shownin FIG. 5A) to the camera is on a vertical line passing throughcantilever 34. In this embodiment, an upper part 44 of this opticalmicroscope is flexibly mounted (via a flexible mount 51) to a focusingstage 45 and a lower part 46 is held by a U-shaped bracket 47 (FIG. 5B),which has two screws 48 and 49 on two of its sides. Two spring plungers(not labeled in FIG. 5B) that push against part 46 opposite to screw 48,and two additional spring plungers in focusing stage 45 push againstpart 46 opposite to screw 49. This arrangement permits the opticalmicroscope to be panned by manually adjusting just two screws 48 and 49.The distance from the pivoting point to the focal plane is over 200 mm,while the panning distance is less than ±0.5 mm. Therefore the maximumvariation of the focal plane during panning is less than 1 μm, which iswithin the focal depth of the optical microscope.

[0036] In contrast to the embodiment illustrated in FIGS. 5A and 5B, insome conventional large sample AFMs (such as TM Microscopes, M5; DigitalInstruments, Dimension 3100; see also U.S. Pat. Nos. 5,463,897 grantedto Prater et al. and 5,705,814 granted to Young et al. both incorporatedby reference herein in their entirety), an oblique mirror is insertedbetween the cantilever and the objective lens. Since an oblique mirrormay have defects and does not fully cover the light path, the quality ofsuch an optical microscope in the prior art is degraded. In order to panthe view with such a prior art optical microscope, the objective lenshad to be moved out of its optical axis, introducing significantblurring. Such blurring is avoided by the embodiment illustrated inFIGS. 5A and 5B, due to the fact that all optical elements—objectivelens, tube lens, and CCD camera—are fixed on a single body, and movetogether during panning, and because of the above-described minimalchange in focal depth during panning.

[0037] The specific embodiment illustrated in FIGS. 5A and 5B has thefollowing advantages (although other embodiments may have fewer orgreater advantages): 1) Scan accuracy: there is no cross talk betweenthe x-y and z axes, and we can achieve high scan accuracy. 2) Samplesize: since the sample is scanned only in x-y direction, large samplesas well as small samples can be scanned at sufficiently high speed. 3)Scan speed: since z scanner has high resonance frequency with highforce, while it need to scan only the cantilever and PSPD, the z servofrequency response is much greater than in the prior art. 4)Convenience: the laser beam aligning mechanism is fixed on a probinghead, to allow such mechanism to be sufficiently large for convenientand precise adjustment without any tools. 5) Optical vision: since thereis enough clearance above the cantilever, it is possible to accommodatea direct on-axis optical microscope. 6) Panning: by using a single bodyoptical microscope with a bracket, the image of optical microscoperemains at high quality.

[0038] In one embodiment, a kinematic probe mounting mechanism, usesmagnets to hold a cantilever chip as shown in FIGS. 6A-6F. A probe arm61 is attached to z scanner 10. Three balls 62-64 and two magnets 65 and66 are mounted at the end of probe arm 61 as shown in FIG. 6B. Oneexample of this embodiment uses two ruby balls 62 and 64 and onehardened stainless steel ball 63 for wear resistance. The stainlesssteel ball is for the electrical contact of the cantilever with a signalline 68. The height of the steel ball 63 is slightly lower than the rubyballs 62 and 64 and the height of the magnets 65 and 66 is slightlylower than the steel ball 63 as shown in FIG. 6C. The magnets 65 and 66are small disk shaped neodymium and mounted in opposite polarity forstronger holding force. The cantilever chip 69 is attached on a chipmount 70, which is a thin mu metal plate with a hole 71 and a slot 72 asshown in FIG. 6D.

[0039] When the chip mount 70 is inserted into an appropriate locationat the end of probe arm 61, the two ruby balls 64 and 62 contact withthe hole 71 and the slot 72 respectively, while the steel ball 63contacts a flat surface of the chip mount 70 to provide kinematicmounting in a reliable manner. The heights of three balls and themagnets are arranged in one implementation such that only the balls makecontact with the chip mount, while the magnets do not contact the chipmount but come close enough to hold the chip mount with the magneticforce. The width of the chip mount 70 is slightly wider than the probearm 61. This design of greater chip mount width allows easy replacementof chip mount 70 (and therefore cantilever chip 69) by holding the sideof the chip mount with bare hand.

[0040] The embodiment described above in relation to FIGS. 6A-6D has thefollowing advantages: 1) With the magnetic holder, it is easier toreplace the chip mount and does not require any tools. 2) The positionof the chip mount is determined by the two ruby balls. Since the span ofthe two ruby balls is wider than in the case of 3 slot/3 ballarrangement for a given chip mount dimension, this particular design hasa superior reproducibility in the probe position. 3) In non-contact modeAFM, the cantilever is normally vibrated by a modulator 67. In thisdesign, the vibration from the modulator is directly delivered to thecantilever chip through the stainless steel ball, which is just abovethe cantilever chip. This is advantageous compared to the 3 slot/3 ballarrangement, where the cantilever is mounted between two slots. Thevibration is delivered to the cantilever through the thin chip mountplate itself, which can cause spurious vibration modes.

[0041] A tightening mechanism of a dovetail assembly of the probe head36 with z stage 73 is illustrated in FIGS. 7A-7D. A bottom dovetail rail74 is rigidly mounted on the z stage 73. A top dovetail rail 75 has aflexure structure 76 as shown in FIG. 7C. The upper portion 77 of topdovetail rail 75 is rigidly mounted on the z stage but the lower portion78 can be pushed down by the two screws on each end of the top rail. Thescrew on the left has a normal right-handed thread, while the screw onthe right side has a left-handed thread. Each screw has a removablehandle, which can be slid out and re-inserted in any of twelve possibleangles as shown in FIG. 7D. A user can select any appropriate angle suchthat the last 90° turn makes firm clamping (or releasing) of the topdovetail rail 78 against the head 36.

[0042] Numerous modifications and adaptations of embodiments describedherein will be apparent to the skilled artisan in view of thedisclosure.

[0043] Accordingly, numerous modifications and adaptations of theembodiments described herein are encompassed by the attached claims.

What is claimed is:
 1. A scanning probe microscope comprising: astationary frame; a first scanner attached to the stationary frame, anda sample chuck attached to the first scanner, the sample chuck beingmovable by the first scanner in a plane; a second scanner physicallydetached from the first scanner and attached to the stationary frame; acantilever supported by the second scanner, and a probe tip attached toa free end of the cantilever, the cantilever being movable by the secondscanner along a line perpendicular to the plane of movement of thesample chuck.
 2. The scanning probe microscope of claim 1 furthercomprising: a reflector located on the cantilever; a light source aimedat the reflector; and a photodetector positioned to receive a portion oflight from the light source reflected by the reflector.
 3. The scanningprobe microscope of claim 2 wherein: the photodetector is mounted on thesecond scanner.
 4. The scanning probe microscope of claim 2 wherein: thephotodetector is mounted on a stage, and the stage is mounted on thestationary frame; the light source is mounted on the stage; and thesecond scanner is mounted on the stage.
 5. The scanning probe microscopeof claim 1 further comprising: an objective lens and a camera supportedby the stationary frame, along the line of movement of the probe tip. 6.The scanning probe microscope of claim 1 wherein: the second scannercomprises a stacked piezoelectric actuator.
 7. The scanning probemicroscope of claim 1 further comprising: a mirror supported by thestationary frame, at a fixed location relative to movement of the probetip provided by the second scanner.
 8. The scanning probe microscope ofclaim 7 wherein: the mirror is oriented parallel to the line of movementof the probe tip.
 9. The scanning probe microscope of claim 7 wherein:the mirror is oriented at an angle relative to the line of movement ofthe probe tip.
 10. The scanning probe microscope of claim 9 wherein themirror is hereinafter “first mirror,” and the microscope furthercomprises: a second mirror supported by the stationary frame, parallelto the first mirror.
 11. The scanning probe microscope of claim 10wherein: each of the first mirror and the second mirror are located onopposite sides of the predetermined straight line.
 12. The scanningprobe microscope of claim 11 further comprising: a photodetectorpositioned opposite to the second mirror, to receive light from thelight source reflected by a reflector located on the cantilever, thefirst mirror and the second mirror.
 13. The microscope of claim 1wherein: the first scanner comprises an x-y flexure stage.
 14. Themicroscope of claim 1 wherein: the sample chuck is movable by the firstscanner only in a plane; and the fixed end of the cantilever is movableby the second scanner only in a direction perpendicular to the plane ofmovement of the sample chuck by the first scanner.
 15. A microscopearrangement comprising: a scanner mounted on a stage, the scanner beinglimited to linear motion in the direction of motion of the stage; acantilever supported by the scanner, the cantilever having a free end;and an objective lens supported by the stage, the lens having an axisparallel to the direction of motion of the stage.
 16. The microscopearrangement of claim 15 further comprising: a reflector supported by thestage between the cantilever and the objective lens, along a lineparallel to the axis of the objective lens, the line passing through thefree end of the cantilever; and a source of light aimed at the reflectorand laterally offset from the axis, the source of light being supportedby the stage.
 17. The microscope arrangement of claim 15 wherein: theaxis of the lens is coincident with the line.
 18. The scanning probemicroscope of claim 15 further comprising: a reflector located on thecantilever; a light source aimed at the reflector; and a photodetectorpositioned to receive a portion of light from the light source reflectedby the reflector.
 19. A method for evaluating a sample, the methodcomprising: moving a probe tip attached to a free end of a cantilever ina first direction; moving a sample in a plane perpendicular to the firstdirection, without moving the probe tip; and measuring deflection of thecantilever during at least one of the acts of moving.
 20. The method ofclaim 19 further comprising: moving a photodetector simultaneously withmoving of the probe tip, wherein a distance of movement of thephotodetector is identical to the distance of movement of the probe tip;wherein a steering mirror is kept stationary during movement of each ofthe probe tip and the photodetector.